1. Field of the Invention
The invention relates in general to a compact disk (CD) recording end address compensation method, and more particularly to the compensation method to avoid the overlapping or staggering defects of recording data on a disk.
2. Description of the Related Art
In the age of technology, an increase in the amount of information, such as the documents, software, MP3, digital pictures and images, demands a high-density storage media. The optical disk such as compact disk (CD-R/CD-RW) and optical disk drives permit the recording of a vast amount of information, thus draw attention for its use as an inexpensive high density and high capacity recording system. However, the reliability of optical disk drive or disk quality could have the effects on the recorded information/data. For example, if the data in a session are recorded by different optical disk drives, the recorded data might be overlapped or staggered due to the differences in performance of optical disk drives. Also, the overlapped or staggered data could still occur while the data are recorded by one optical disk drive with unstable recording quality. The missing pieces of data cannot be retrieved permanently.
CD-R/CD-RW disk contains time-code information called ATIP. ATIP is abbreviation of “Absolute Time In Pre-groove”, which means address and recording information encoded in the wobble groove on CD-R and CD-RW media. Based on this information, an optical disk drive (burner) can determine the absolute position in Pregroove. After recording/writing, data are written in CD format synchronizing with ATIP, and this CD coding system including a clock which monitors recording time and predicts a total is so-called “A-time” (Absolute-Time). The A-time address is encoded in Q-channel (Sub-channel) and called “Q-code” (Sub-code) thereinafter. The recording information is recorded in accordance with the time-code information of ATIP, while the recording information is read in accordance with the time-code information of Q-code. Simply saying, the ATIP address and Q-code address are referred to the recording position and reading position, respectively.
FIG. 1 is a schematic showing a normal relationship between the Q-code address and the ATIP address. In the normal recording condition, one Q-code address corresponds to one ATIP address. If it is desirable to read the data corresponded to Q-code address of 8 (Q-code=8), for example, the data encoded in the ATIP address of 8 will be acquired by transformation. Typically, the recording (writing) information in CD-R/CD-RW is continuously performed at a period of time. However, the recording defects such as excursion of the spin motor may occur, and the differences in rotation frequency of recording media will cause the overlapped or staggered recording data.
FIG. 2 is a schematic showing an abnormal relationship between the Q-code address and the ATIP address while the recording data are overlapped. In FIG. 2, data are actually encoded in 9 blocks of ATIP (ATIP address: 0˜8), but it only shows 8 blocks of Q-channel (Q-code address: 0˜7) are encoded. Since the CD coding system predicts a total according to Q-code, it starts to record the next data from the Q-code address of 8 (corresponding to ATIP address of 8), and the ATIP address of 8 will be used again. The phenomenon as shown in FIG. 2 is called “Q-delay”, and the overlapped recording data cannot be retrieved again. One of the reasons for “Q-delay” is that the rotation speed of the spindle motor has been slowed down.
FIG. 3 is a schematic showing an abnormal relationship between the Q-code address and the ATIP address while the recording data are staggered. In FIG. 3, data are actually encoded in 10 blocks of ATIP (ATIP address: 0˜9), but it shows 11 blocks of Q-channel (Q-code address: 0˜10) are encoded. Since the CD coding system predicts a total according to Q-code, it starts to record the next data from the Q-code address of 11 (corresponding to ATIP address of 11), and the ATIP address of 10 will be blank. The phenomenon as shown in FIG. 3 is called “Q-lead”, and the blank area of ATIP has effect on the data retrieve. One of the reasons for “Q-lead” is that the rotation speed of the spin motor has been speeded up.
Whether the phenomenon of “Q-delay” or “Q-lead” arises, it has undesirable effect on the recording result. For example, if the data of music files are overlapped, the software for playing the digital media will try to read the data at the overlapped section back (“read error” or “C2 error”). The next music won't be played until the music file is selected manually. If the data of music files are staggered thus resulting in the blank blocks on the track, an uncorrectable error still arises, though the blank blocks has no significant meaning for music recording.
In addition, the information of file structure on the data track could be ruined due to the phenomenon of “Q-delay” or “Q-lead”. Session is a contiguous area of the disk that contains a Lead-in, Program Area, and Lead-out. Lead-In marks the start of each session on the disk, and Lead-Out marks the end of each session on the disk. The main channel in the Lead-in area contains audio or data null information. This area is coded as track zero. The Q Sub-channel in this Lead-in area is coded with the Table of Contents information. The main channel in the Lead-out area contains audio or data null information. Couple of blocks right before the Lead-out area contains file structure information, such as folder name, file name. If the Q-code address mismatches the ATIP address, file structure information in those blocks could be ruined and unable to be found.
Accordingly, it is one of important goals for the engineers not only to ensure that the desirable data can be recorded without missing any piece, but to exclude the possibility of discontinues record.